问题：写出一个链式调用，实现Chain().users('michael').repos 的输出结果是/users/michael/repos

答案：

class Chain(object):

    def __init__(self, path=''):

        self._path = path

    def __getattr__(self, attr):

        return Chain('%s/%s' % (self._path, attr))

    def __call__(self, name):

        return Chain('%s/%s' % (self._path, name))

    def __str__(self):

        return self._path

    __repr__ = __str__